LM Thunderdome in detail
About the LM Thunderdome engine
The MB&F Legacy Machine Thunderdome is the culmination of four years of development, an unprecedented collaboration between two of the most admired horological minds today, Eric Coudray and Kari Voutilainen. While the technical construction originated with Coudray, it was Voutilainen who translated the mechanism into the aesthetically refined movement that inhabits LM Thunderdome.
Though the latter task may seem straightforward compared to technical development, it actually entails a far greater level of difficulty than is implied. The complex and delicate relationship between the 413 components of the LM Thunderdome engine makes every micro-adjustment an extended exercise in mechanical reconfiguration. With a movement diameter of only 35mm, proportionate design is exponentially emphasised and there is far less margin for error. A bridge that is even one single millimetre too wide, or a pinion moved just a few micrometres to either side, would immediately stand out, glaringly out of place.
Says Voutilainen, “In such a complex project, with so many different considerations, I chose the traditional method of hand-drawing the movement rather than working with computer software. It allowed me to have a much better feel for the proportions and the choices that needed to be made about aesthetics and function.”
Appearing to hover above the dial plate of Legacy Machine Thunderdome is the ‘TriAx’, a highly sophisticated multi-axis rotating escapement that is completely novel even in Eric Coudray’s unmatched oeuvre of similar mechanisms.
There are three axes rotating at different speeds and on different planes, starting with the innermost axis that makes one complete turn in 8 seconds. The next axis of rotation is canted at right angles to the first, and makes one complete turn in 12 seconds. The outermost axis of rotation is canted at right angles to the second, and makes one complete turn in 20 seconds. This gives LM Thunderdome the distinction of possessing the fastest combined rotation in the category of multi-axis regulating mechanisms.
Additionally, the last axis of rotation is excentric relative to the other two, such that the final motion of the balance wheel, when viewed in isolation, is most precisely described as an orbital tri-axial rotation.
In chronometric context, this means the LM Thunderdome engine has the largest range and fastest rate of balance positional displacement known throughout the history of watchmaking. In a rather more accessible context, this means that LM Thunderdome offers a visual spectacle that the horological world has never seen before.
Existing terminology does not adequately cover the rotating mechanism of LM Thunderdome. The current separation of rotating escapements into tourbillon or karrusel categories does not work here, as Coudray’s creation incorporates key elements of both, such as the split-train energy transmission of the karrusel, and the fixed wheel of the tourbillon. Even so, these elements are configured in ways that are unfamiliar to our conventional definitions of tourbillon and karrusel. Mechanically speaking, Thunderdome stands alone.
Driving this cinematic feat of horology, which weighs close to 1g, is a manual-winding three-barrel movement with 45 hours of power reserve.
More about TriAx: a three-dimensional balance and a rare escapement
For the first time in any micro-mechanical work of horology, a hemispherical balance is used to provide inertia in the regulating organ. This completely innovative custom solution allows for the largest possible balance when combined with a cylindrical hairspring, while still maintaining a relatively compact cage (or compound cages, as the case might be).
Cylindrical hairsprings have been used throughout history for timepieces that prioritised isochronism and overall timekeeping performance, since the highly uniform breathing of a cylindrical hairspring is less likely to cause timekeeping anomalies even in a wide range of disruptive environmental conditions.
Pioneering a three-dimensional balance might be considered by even the most ambitious watchmakers as enough of a challenge, without the extra step of planting it in the middle of a multi-axis rotating mechanism. How does one adjust a balance that takes a different position in all three dimensions every second?
Even state-of-the-art laser measuring instruments were baffled by the continuously shifting balance and its enclosing rotating cages. MB&F furthered the known applications of this laser technology by shifting the beam frequency entirely into the infra-red range (thus avoiding any misreadings caused by the visible range of the beam interacting with the polished components) and developing a system of taking discrete readings at specific intervals over a period of time. This, in addition to the combined experience and skill of Eric Coudray and the MB&F watchmakers, allowed the LM Thunderdome balance to be adjusted with efficiency and precision.
The key to the high-speed rotation of TriAx at the heart of LM Thunderdome is a little-known variant of escapement, first proposed by 19th-century American watchmaker and inventor Albert H. (not Harry) Potter as a tourbillon modification. Instead of driving the escape wheel, via its pinion, around a fixed fourth wheel, he made the escape wheel the fixed wheel, and altered the geometry of the escape lever accordingly. This, he correctly theorised, would allow blindingly fast tourbillon rotational speeds.
In the TriAx mechanism of LM Thunderdome, the Potter escapement is modified yet further. Instead of a fixed escape wheel with externally oriented teeth, co-axial to the balance, Thunderdome uses a fixed escape wheel with inverted teeth, co-planar to the lever fork. Only once has this configuration been seen in modern horology, and only in a single-axis tourbillon, never before in a multi-axis mechanism. There was no rulebook or established precedent, so TriAx created its own.
These are all firsts for MB&F, and more significantly, they are firsts in the horological world.